1. Field
The following description relates to a lens driving unit for an optical pickup, and more particularly, to a magnetic circuit of an actuator of a lens driving unit.
2. Description of Related Art
A typical object lens driving unit of an optical pickup has a voice coil motor (VCM). The object lens driving unit has a static structure, including a permanent magnet and a yoke, and has a moving structure, including a driving coil and an object lens. In general, the moving structure is supported by a plurality of suspension wires. The suspension wires have an electrical connection function for applying a driving voltage to a driving coil to control focusing and tracking of a lens.
In order to properly fit therein, an optical pickup for a slim-type optical disc drive that is used for a notebook computer needs to have a limited thickness. The limit on thickness leads to a limit on the amount of weight and parts that can be used for the optical pickup. Accordingly, the optical pickup typically has a low strength. For example, the optical pickup for a slim-type optical disc drive may be formed of light material because a higher driving current is required as a weight of a lens frame is increased. Typically an optical pickup is formed of a light plastic.
However, a lens frame formed of a light plastic is structurally unsound and may warp easily due to concentrated electromagnetic force and tracking electromagnetic force applied diagonally to the lens frame. The warpage of the lens frame may result in malfunction such as tracking and focusing delays.